[Halld-tracking-hw] Preamps

[Fernando J. Barbosa]

Hi Naomi,

Now it makes sense. The original preamp had a gain of 1.5 mV/fC and the 
new one that you have is 0.57 mV/fC. So, a factor of 2.63 lower now. 
This seems to be confirmed on the first set of plots if you were to cut 
the "overflows" from the left plot (just by looking at the plot).

The dynamic range on the old preamp was wider with 400 fC at the 1% 
level; the new preamp is at 380 fC @ 5% (for your configuration). The 
older preamp had a much wider DR with a smooth roll off before hard 
saturation; the new preamp has  narrower  DR before hard saturation. It 
is important to keep in mind that we want to operate in the linear 
region, perhaps even better than the 5% level. This is seen on the next 
sets of plots for the new preamp has a hard saturation at ~2100 
channels. The fADC125 will be optimized to have this mapped to the upper 
level of its 12-bit range.

I cannot say much about the energy plots because of non-linearity and 
saturation on both old and new preamps. The detector gain is too high 
and I suggest that you take additional runs starting at 1750V.

Thanks and best regards,
Fernando




Naomi Jarvis wrote:
>
> Hello,
>
> I just wanted to correct something I wrote yesterday (which did not 
> make sense anyway).  From looking at the scope traces with the 55Fe 
> source I thought that the new preamp gain was less than that of the 
> old preamp.  After actually collecting data and extracting amplitude 
> histograms it turned out that the preamp output was in fact 
> saturating, although I could not see this on the scope.  I thought I 
> could distinguish between saturated and non-saturated traces, but 
> evidently this was not the case.   So I have added some 55Fe plots to 
> the wiki:
>
> http://www.jlab.org/Hall-D/software/wiki/index.php/Preamp_4:_Comparison_of_55Fe_data_with_original_preamp 
>
>
> These are again comparing the two preamps, and to be clear, the only 
> difference between the two sets of runs is that the preamps are 
> switched and the baseline on the shaper is set to  approx -130mV 
> (because the preamps have a different baseline).  Everything else is 
> the same, both sets of data were taken on the same day.
>
> Is there anything else you would like me to try with it tomorrow, or 
> leave counting over the weekend?
> Naomi.
>
>
>
> Fernando J. Barbosa wrote:
>> Hi all,
>>
>> It seems that Monday @ 10 is preferable to most.
>>
>> Gerard, I will discuss with you any issues related to the preamps and 
>> ASICs afterwards.
>>
>> In preparation for the meeting, I suggest reviewing GlueX docs 1070, 
>> 1079 and 1364. I will send an email with the agenda for the meeting 
>> by the end of the week.
>>
>> Thanks and best regards,
>> Fernando
>>
>> Curtis A. Meyer wrote:
>>> Monday at 10:00am would be great!   Curtis
>>> On 6/9/10 2:31 PM, Fernando J. Barbosa wrote:
>>>> Hi Curtis,
>>>>
>>>> Would Monday @ 10  next week work for everyone?
>>>>
>>>> Best regards,
>>>> Fernando
>>>>
>>>>
>>>>
>>>> Curtis A. Meyer wrote:
>>>>> Hi Fernando
>>>>>
>>>>>   the next tracking meeting is not until June 23, so if we wait 
>>>>> until then to discuss this
>>>>> issue, we will certainly fail to meet your deadline of June 25. It 
>>>>> also takes several days
>>>>> of cosmic running to get a data point, so checking anything also 
>>>>> takes time. If there is any
>>>>> way that we could have a meeting next week, it would help speed 
>>>>> things along.
>>>>>
>>>>>   thanks - Curtis
>>>>>
>>>>>
>>>>> On 6/9/10 12:55 PM, Fernando J. Barbosa wrote:
>>>>>> Hi Naomi,
>>>>>>
>>>>>> I suggest we reserve part of the next tracking meeting to discuss 
>>>>>> these issues.
>>>>>>
>>>>>> Let me also take the opportunity to emphasize that the CDC and 
>>>>>> the FDC groups must finalize their measurements so that the 
>>>>>> procurement of the ASICs is not impacted. This means that I would 
>>>>>> like to close this project by 25 June 2010.
>>>>>>
>>>>>> Thanks and best regards,
>>>>>> Fernando
>>>>>>
>>>>>>
>>>>>> Naomi Jarvis wrote:
>>>>>>>
>>>>>>> Good morning!
>>>>>>>
>>>>>>> I would like to talk about the new preamp but I don't think 
>>>>>>> there will be enough time in our tracking mtg this morning.
>>>>>>> The concerns are that the preamp output is topping out at around 
>>>>>>> 500 mV even with the cosmics, and the gain for cosmics seems to 
>>>>>>> have increased, whereas for Fe55 it was ~1/3 less.
>>>>>>>
>>>>>>> I put one page on the wiki      
>>>>>>> http://www.jlab.org/Hall-D/software/wiki/index.php/CDC#Preamp4_.28GlueXdoc1364_Tbl_2_Row_2.29 
>>>>>>>
>>>>>>> The recent cosmic runs there took a week each, and were with the 
>>>>>>> chamber flat, ie 90 degree cosmics.   I'll add more data as it 
>>>>>>> becomes available;  at present it is counting at 2kV.
>>>>>>> Can we set up a time to talk about this next week?   (The rest 
>>>>>>> of this week is out for us; I think the only times we cannot do 
>>>>>>> next week are 1pm Tues + the regular mtg on Wed).
>>>>>>>
>>>>>>> Thanks,
>>>>>>>
>>>>>>> Naomi.
>>>>>
>>>>>
>>>
>>>
>
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